How to Fix a Windows PC That Won’t Boot — A Decision Tree

A PC that won’t boot is one failure with about eight possible causes, and most guides throw all eight at you in a list. That’s why people end up reinstalling Windows over what turns out to be a loose cable or a bad update.

This guide is a decision tree instead. Start at the top, answer one question, and it sends you to the right branch. Work through it in order and you’ll either fix it or know exactly what’s broken — without wiping anything you didn’t need to.

Start here: what actually happens when you press the power button?

Branch A — no signs of life at all

Nothing lights up, no fan noise. This is almost always power, and it’s the cheapest branch to rule out.

If there’s genuinely nothing after all of that, you’re looking at a power supply or motherboard fault. On a desktop the PSU is the cheaper and more likely of the two.

Branch B — powers on but nothing on screen

Fans spin, lights come on, but no manufacturer logo. The machine isn’t getting through POST — the self-check that runs before Windows is involved at all. Nothing here is a Windows problem.

• Check the obvious display path first — monitor powered, correct input selected, cable in the graphics card rather than the motherboard if you have a discrete GPU.
• Listen and look for beep or LED codes. Most motherboards signal the failing component. Look the pattern up against your board’s manual — this often takes you straight to the answer.
• Reseat the RAM. Remove all sticks, put one back in the slot the manual specifies for single-stick operation, and try. RAM that has crept loose is one of the most common causes.
• Disconnect everything non-essential — extra drives, USB devices, expansion cards. Boot with CPU, one stick of RAM and the boot drive only.

Branch C — logo appears, then it stops or loops

You see the manufacturer logo, so hardware is broadly alive. Windows is failing to start. This is where Windows Recovery Environment (WinRE) becomes your main tool.

Getting into WinRE when Windows won’t start

Windows watches for repeated boot failures. Interrupt the boot three times — power on, and as soon as you see the logo, hold the power button until it powers off — and on the fourth attempt it should come up in Recovery.

If that doesn’t work, boot from Windows installation media on a USB stick and choose Repair your computer rather than Install. It’s worth making one of these before you need it.

What to try, in order

The boot rebuild commands, run from WinRE’s Command Prompt in this order:

bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

On a UEFI system bootrec /fixboot commonly returns “Access is denied”. That’s expected rather than a fault — the EFI partition isn’t mounted. It’s recoverable, but at that point you’re deep enough that recovering your data and reinstalling is often faster than continuing.

If you would rather see the recovery menu being reached in practice, this walkthrough covers five different routes into Advanced Startup Options on Windows 10 and 11:

Branch D — Windows starts, then blue screens

You get the Windows logo and spinner, then a blue screen, possibly on a loop. Windows is loading far enough to run drivers, and one of them is failing. Write down the stop code — it narrows this dramatically.

Safe Mode is the tool here, because it loads a minimal driver set. From WinRE: Troubleshoot, then Advanced options, then Startup Settings, then Restart, then press 4 or 5.

If Safe Mode works, the problem is something Safe Mode isn’t loading — a third-party driver or a startup program. Roll back or remove whatever you installed most recently, particularly graphics, storage or antivirus drivers. Then run:

sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth

Run them in that order, and run sfc /scannow again afterwards — DISM repairs the component store that SFC pulls its replacement files from, so the second pass can fix things the first couldn’t.

Branch E — reaches the login screen, then fails

If you’re getting to login, the boot chain is healthy and you have a software problem — which is much better news. Check for a corrupted user profile (try another account), disable startup programs via Task Manager in Safe Mode, and check Event Viewer under Windows Logs then System for errors around the failure time.

Before you repair anything: get your data out

If there’s any chance the drive is failing — clicking noises, the drive not appearing in firmware, repeated read errors — copy your data off before attempting repairs. Repair operations write to the disk, and writing to a failing drive can turn a recoverable situation into an unrecoverable one.

The simplest route: boot from a Linux live USB, mount the Windows drive, and copy what matters to an external disk. No installation, no changes to the failing drive.

Glossary

Frequently asked questions

How do I force Windows into recovery mode if it won’t boot?

Interrupt the boot three times by holding the power button as soon as the logo appears. On the fourth attempt Windows should start Recovery automatically. Failing that, boot from installation media and choose Repair your computer.

Will Startup Repair delete my files?

No. Startup Repair only touches boot configuration. Reset and Clean Install are the options that affect your files, and both warn you first.

Why does my PC keep looping through Automatic Repair?

Because the underlying fault isn’t a boot configuration one, so the repair fails and Windows tries again. Common causes are a failing drive, corrupted system files or a bad driver. Break the loop by entering WinRE and using System Restore or uninstalling the last update instead.

Is it worth trying a different SATA or power cable?

Yes, and it’s worth doing early. Cables are the cheapest thing to eliminate, and a drive that doesn’t appear in firmware because of a marginal cable looks exactly like a dead drive.

How do I know if it’s the drive that’s failed?

Check whether the drive appears in your firmware setup. If it isn’t listed there, Windows was never going to find it. Clicking or grinding from a mechanical drive is a definite failure sign — power it down and prioritise data recovery over repair.

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